The semiconductor manufacturing industry is continually striving to manufacture smaller, faster and more reliable semiconductor devices. At the present time, hybrid integrated circuits are used in a number of application requiring precision circuit operation. Such circuits are typically fabricated by forming thin film resistors, interconnect metals, and bonding pads on an insulating substrate. Presently resistors are typically defined by a layer of tantalum nitride. In such instances, gold and similar interconnect materials have been used to form the interconnects to these resistors. However, fabrication of these resistors may be problematic.
For example, in its efforts to develop smaller, faster and more reliable semiconductor devices, the semiconductor manufacturing industry has looked for other interconnect structures than those based on gold. For instance, aluminum interconnects have been seen as viable, faster and more reliable alternatives.
The incorporation of thin film resistors into present day integrated circuits poses a substantial problem because of the extensive use of aluminum as the choice interconnect material. The major problem of incorporating a thin film resistor into an integrated circuit employing aluminum interconnects lies in the incompatibility of the material from which the thin film resistor is made with the etching chemistry used to form the aluminum interconnects. More specifically, the etching chemistry can attack the resistor material and either destroy the resistor altogether or significantly degrade the resistor's reliability. For example, traditional thin film resistor devices are not compatible with chemistries including hydrogen chloride, hydrogen fluoride or other fluorine containing chemicals, oxygen plasma, some photoresist strippers and many more similar chemistries. As is well known, aluminum is often patterned using a dry plasma etch, which negatively affects the thin film resistor device. Thus, without specifically constructing semiconductor manufacturing tools compatible with gold interconnects or redesigning the traditional thin film resistor devices, reliability problems will continue to exist when trying to incorporate a thin film resistor into an integrated circuit formed with aluminum interconnects.
Accordingly, what is needed in the art is a thin film resistor device that is adapted to accept the change from gold and copper interconnects to aluminum interconnects, and does not experience the reliability issues experienced when combining the prior art thin film resistors and aluminum interconnect structures.